Vitamin D, a neuro-immunomodulator: implications for neurodegenerative and autoimmune diseases

Circadian rhythm and cartilage extracellular matrix genes in osseointegration: a genome-wide screening of implant failure by vitamin D deficiency

BACKGROUND

Successful dental and orthopedic implants require the establishment of an intimate association with bone tissue; however, the mechanistic explanation of how biological systems accomplish osseointegration is still incomplete. We sought to identify critical gene networks involved in osseointegration by exploring the implant failure model under vitamin D deficiency.

METHODOLOGY

Adult male Sprague-Dawley rats were exposed to control or vitamin D-deficient diet prior to the osteotomy surgery in the femur bone and the placement of T-shaped Ti4Al6V implant. Two weeks after the osteotomy and implant placement, tissue formed at the osteotomy site or in the hollow chamber of T-shaped implant was harvested and total RNA was evaluated by whole genome microarray analyses.

PRINCIPAL FINDINGS

Two-way ANOVA of microarray data identified 103 genes that were significantly (>2 fold) modulated by the implant placement and vitamin D deficiency. Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses assigned the highest z-score to the circadian rhythm pathway including neuronal PAS domain 2 (NPAS2), and period homolog 2 (Per2). NPAS2 and Aryl hydrocarbon receptor nuclear translocator-like (ARNTL/Bmal 1) were upregulated around implant and diminished by vitamin D deficiency, whereas the expression pattern of Per2 was complementary. Hierarchical cluster analysis further revealed that NPAS2 was in a group predominantly composed of cartilage extracellular matrix (ECM) genes. Whereas the expression of bone ECM genes around implant was not significantly affected by vitamin D deficiency, cartilage ECM genes were modulated by the presence of the implant and vitamin D status. In a proof-of-concept in vitro study, the expression of cartilage type II and X collagens was found upregulated when mouse mesenchymal stem cells were cultured on implant disk with 1,25D supplementation.

CONCLUSIONS

This study suggests that the circadian rhythm system and cartilage extracellular matrix may be involved in the establishment of osseointegration under vitamin D regulation.

Vitamin D, neurocognitive functioning and immunocompetence

PURPOSE OF REVIEW

Vitamin D deficiency is recognized as one of the most common medical conditions in children and adults. The major causes are inadequate sun exposure and inadequate intakes of dietary and supplemental vitamin D. Vitamin D deficiency and insufficiency defined as a 25-hydroxyvitamin D level less than 20 and 21-29 ng/ml, respectively, have been linked to increased risk for a variety of medical conditions including cancer, heart disease, type II diabetes, infectious diseases, autoimmune diseases, metabolic bone diseases and neurological disorders.

RECENT FINDINGS

The skeletal muscle and brain have a vitamin D receptor and the central nervous system has a capacity to activate vitamin D. Low vitamin D status has been linked to poor performance in neurocognitive testing in elderly. Vitamin D deficiency has been associated with muscle weakness, depression, schizophrenia, Alzheimer's disease, multiple sclerosis and a lower motor neuron-induced muscle atrophy.

SUMMARY

Correcting vitamin D deficiency and preventing vitamin D deficiency in children and adults should be a high priority for healthcare professionals to reduce risk for a wide variety of neurological disorders. Children and adults should take at least 400 international unit IU and 2000 IU vitamin D/day, respectively, to prevent vitamin D deficiency and insufficiency.

Vitamin D and multiple sclerosis: what are the guidelines for a reliable clinical trial?

Evaluation of: Mowry EM, Krupp LB, Milazzo M et al. Vitamin D status is associated with relapse rate in pediatric-onset multiple sclerosis. Ann. Neurol. 67, 618-624 (2010). In 1960, Sir Donald Acheson suggested a link between multiple sclerosis and solar radiation. Some 50 years and numerous studies later, there is still no certainty about the role of UV or vitamin D, the sun-induced hormone, on the course of multiple sclerosis. In order to further clarify this issue, the article by Mowry et al. assesses the level of vitamin D in patients at the time of multiple sclerosis onset and correlates it with the number of subsequent clinical relapses. The conclusion is that every 10 ng/ml increase in the adjusted vitamin D level is associated with a 34% decrease in the rate of relapse. This result reinforces the rationale for a randomized double-blind placebo-controlled clinical trial. Several criteria for a well-designed trial are proposed.

Malformation syndromes caused by disorders of cholesterol synthesis

Cholesterol homeostasis is critical for normal growth and development. In addition to being a major membrane lipid, cholesterol has multiple biological functions. These roles include being a precursor molecule for the synthesis of steroid hormones, neuroactive steroids, oxysterols, and bile acids. Cholesterol is also essential for the proper maturation and signaling of hedgehog proteins, and thus cholesterol is critical for embryonic development. After birth, most tissues can obtain cholesterol from either endogenous synthesis or exogenous dietary sources, but prior to birth, the human fetal tissues are dependent on endogenous synthesis. Due to the blood-brain barrier, brain tissue cannot utilize dietary or peripherally produced cholesterol. Generally, inborn errors of cholesterol synthesis lead to both a deficiency of cholesterol and increased levels of potentially bioactive or toxic precursor sterols. Over the past couple of decades, a number of human malformation syndromes have been shown to be due to inborn errors of cholesterol synthesis. Herein, we will review clinical and basic science aspects of Smith-Lemli-Opitz syndrome, desmosterolosis, lathosterolosis, HEM dysplasia, X-linked dominant chondrodysplasia punctata, Congenital Hemidysplasia with Ichthyosiform erythroderma and Limb Defects Syndrome, sterol-C-4 methyloxidase-like deficiency, and Antley-Bixler syndrome.

Cognitive and emotional processing associated with the Season of Birth and dopamine D4 receptor gene

The 7-repeats variant of the dopamine D4 receptor (7R) VNTR polymorphism has been associated with higher novelty seeking (NS) and disadvantageous decision making in the Iowa Gambling Task (IGT). Season of Birth (SOB) is a significant determinant of NS. SOB and L-DRD4 genetic polymorphism may independently and interactively influence similar behaviors through their common effects on the dopaminergic system. Two hundred and twenty-seven healthy males grouped in summer-born/4-repeats (4R) (n=75), winter-born/4R (n=90), summer-born/7R (n=31) and winter-born/7R (n=31) groups, completed multimodal assessment for personality, planning for problem solving and decision making. Winter-born/7R subjects had significantly worse IGT performance throughout the task compared to 4R individuals, while summer-born 7R subjects had intermediate, although not significantly different performance. Moreover, winter-born/7R subjects had increased behavioral approach to reward without parallel reduction in sensitivity to fear or to social approval cues. The DRD4-by-SOB groups did not differ in planning for problem solving. These results suggest that a DRD4-by-SOB interaction is associated with increased behavioral approach to reward and risk taking but efficient problem solving. In addition, these results further support the hypothesis that SOB modifies the behavioral expression of dopaminergic genetic polymorphism. SOB should be included in future studies of risky behaviors and behavioral genetic studies of the dopamine system.

Severity of experimental autoimmune encephalomyelitis is unexpectedly reduced in mice born to vitamin D-deficient mothers

Accumulating data indicate that vitamin D, a sun-induced hormone, plays a key role in multiple sclerosis (MS) etiology. Notably, it has been shown that there is a remarkable season of birth effect in MS. We surmised that gestational vitamin D deficiency is a risk factor for MS. To test this hypothesis, a vitamin D deficiency was induced in C57BL/6 female mice 6 weeks prior to conception and prolonged until offspring birth. Contrary to our prediction, we show here that adult offspring exposed to developmental vitamin D deficiency (DVD) developed a striking milder and delayed experimental autoimmune encephalomyelitis (EAE), when compared to control offspring. Using reverse transcription and quantitative real-time PCR, we measured the expression level of 22 candidate transcripts in the spleen, the cerebrum and the spinal cord, at Day0 and Day30 post-immunization. We report here that, at Day30 post-immunization, TNF, osteopontin, H2-Eb were over-expressed and IFN was under-expressed in the spinal cord of control mice and not in DVD mice. Another discrepancy between nervous and immune systems was observed: expression of IL4 was dysregulated exclusively in the spleen. Reduced symptom severity in DVD mice can partially be explained by a nervous system-restricted over-expression of vitamin D receptor (VDR), two heat shock proteins (HSP90, HSPa8) and FK506 binding protein 1a (FKBP1a), at Day0. Our clinical test and molecular findings converge to indicate that maternal hypovitaminosis D imprints the foetus and alters the susceptibility of the offspring to EAE. We propose a new hypothesis to explain our unexpected observations.

Serum 25-hydroxyvitamin D and depressive symptoms in older women and men

CONTEXT

Hypovitaminosis D and depressive symptoms are common conditions in older adults.

OBJECTIVE

We examined the relationship between 25-hydroxyvitamin D [25(OH)D] and depressive symptoms over a 6-yr follow-up in a sample of older adults.

DESIGN AND SETTING

This research is part of a population-based cohort study (InCHIANTI Study) in Tuscany, Italy.

PARTICIPANTS

A total of 531 women and 423 men aged 65 yr and older participated.

MAIN OUTCOME MEASURE

Serum 25(OH)D was measured at baseline. Depressive symptoms were assessed at baseline and at 3- and 6-yr follow-ups using the Center for Epidemiological Studies-Depression Scale (CES-D). Depressed mood was defined as CES-D of 16 or higher. Analyses were stratified by sex and adjusted for relevant biomarkers and variables related to sociodemographics, somatic health, and functional status.

RESULTS

Women with 25(OH)D less than 50 nmol/liter compared with those with higher levels experienced increases in CES-D scores of 2.1 (P = 0.02) and 2.2 (P = 0.04) points higher at, respectively, 3- and 6-yr follow-up. Women with low vitamin D (Vit-D) had also significantly higher risk of developing depressive mood over the follow-up (hazard ratio = 2.0; 95% confidence interval = 1.2-3.2; P = 0.005). In parallel models, men with 25(OH)D less than 50 nmol/liter compared with those with higher levels experienced increases in CES-D scores of 1.9 (P = 0.01) and 1.1 (P = 0.20) points higher at 3- and 6-yr follow-up. Men with low Vit- D tended to have higher risk of developing depressed mood (hazard ratio = 1.6; 95% confidence interval = 0.9-2.8; P = 0.1).

CONCLUSION

Our findings suggest that hypovitaminosis D is a risk factor for the development of depressive symptoms in older persons. The strength of the prospective association is higher in women than in men. Understanding the potential causal pathway between Vit- D deficiency and depression requires further research.

Very low levels of vitamin D in systemic sclerosis patients

Vitamin D displays many extraosseous immunomodulatory effects. The aim of the study was to evaluate the level of vitamin D in patients with systemic sclerosis (SSc) and to analyze the associations between the concentration of the vitamin and clinical manifestations. In March-April 2009, 65 consecutive SSc patients underwent evaluation of vitamin D concentrations by the LIAISON immunoassay (normal 30-100 ng/ml). Serum levels between 10 and 30 ng/ml were classified as vitamin D insufficiency, while concentrations <10 ng/ml as vitamin D deficiency. None of the patients were receiving vitamin D supplementation at the time of or during the year prior to study entry. The mean level of vitamin D was 15.8 ± 9.1 ng/ml. Only three cases showed normal values; vitamin D insufficiency and deficiency were found in 43 and 19 cases, respectively. Patients with vitamin D deficiency showed longer disease duration (13.1 ± 6.8 versus 9.4 ± 5.5 years, P = 0.026), lower diffusing lung capacity for carbon monoxide (63.7 ± 12.4 versus 76.4 ± 20.2, P = 0.014), higher estimated pulmonary artery pressure (28.9 ± 9.9 versus 22.8 ± 10.4, P = 0.037) and higher values of ESR (40 ± 25 versus 23 ± 13 mm/h, P = 0.001) and of CRP (7 ± 7 and 4 ± 2 mg/l, P = 0.004) in comparison with patients with vitamin D insufficiency; moreover, late nailfold videocapillaroscopic pattern was more frequently found (52.6% versus 18.6%, P = 0.013). None of the patients showed evidence of overt mal-absorption. Low levels of vitamin D are very frequent in patients with SSc. Intestinal involvement is not likely the cause of vitamin D deficit; other factors such as skin hyperpigmentation and reduced sun exposition for psychological and social reasons may be implicated. Patients with vitamin D deficiency showed more severe disease in comparison with patients with vitamin D insufficiency, above all concerning lung involvement. Further trials are awaited to determine whether vitamin D could represent a modifiable factor able to interfere with SSc evolution.

Microglia activation and anti-inflammatory regulation in Alzheimer's disease

Inflammatory regulators, including endogenous anti-inflammatory systems, can down-regulate inflammation thus providing negative feedback. Chronic inflammation can result from imbalance between levels of inflammatory mediators and regulators during immune responses. As a consequence, there are heightened inflammatory responses and irreversible tissue damage associated with many age-related chronic diseases. Alzheimer's disease (AD) brain is marked by prominent inflammatory features, in which microglial activation is the driving force for the elaboration of an inflammatory cascade. How the regulation of inflammation loses its effectiveness during AD pathogenesis remains largely unclear. In this article, we will first review current knowledge of microglial activation and its association with AD pathology. We then discuss four examples of anti-inflammatory systems that could play a role in regulating microglial activation: CD200/CD200 receptor, vitamin D receptor, peroxisome proliferator-activated receptors, and soluble receptor for advanced glycation end products. Through this, we hope to illustrate the diverse aspects of inflammatory regulatory systems in brain and neurodegenerative diseases such as AD. We also propose the importance of neuronal defense systems, because they are part of the integral inflammatory and anti-inflammatory systems. Augmenting the anti-inflammatory defenses of neurons can be included in the strategy for restoration of balanced immune responses during aging and neurodegenerative diseases.

Developmental vitamin D deficiency alters learning in C57Bl/6J mice

Epidemiological studies have highlighted a season of birth effect in multiple sclerosis and schizophrenia. As a result, low prenatal vitamin D has been proposed as a candidate risk factor for these brain diseases, with cognitive impairments. In order to further investigate the long-term consequences of a transient gestational hypovitaminosis D, we used a mouse developmental vitamin D (DVD) deficiency model. Female C57Bl/6J mice were fed a vitamin D-free diet for 6 weeks prior to conception and during gestation. At birth, dams and their offspring were fed a normal vitamin D-containing diet. The adult offspring underwent a learning test based on olfactory cues, at 30 weeks and 60 weeks of age. In addition, using magnetic resonance imaging (MRI), volumes of cerebrum, hippocampus and lateral ventricles were measured at 30 weeks and 70 weeks of age. We found that DVD-deficient mice, when compared to control animals at Week 30, displayed impaired learning and smaller lateral ventricles. At Weeks 60-70, both groups deteriorated when compared to young mice and no significant difference was observed between groups. This study confirms that transient prenatal vitamin D deficiency alters brain development and functioning and induces cognitive impairments in the young adult offspring.

Nuclear receptors, inflammation, and neurodegenerative diseases

Chronic inflammation is associated with many neurodegenerative diseases, including multiple sclerosis, Parkinson's disease, and Alzheimer's disease. Increasing evidence that neuroinflammation contributes to disease severity has generated considerable interest in determining whether inhibition of inflammation pathways might be of therapeutic benefit. One potential avenue of intervention is provided by members of the nuclear receptor superfamily of ligand-dependent transcription factors that exert anti-inflammatory effects in many cell types. Here, we review recent studies providing insights into the distinct mechanisms that enable nuclear receptors to modulate immune responses, describe inflammatory components of neurodegenerative diseases, and discuss recent literature relevant to roles of nuclear receptors in influencing these processes.

Neuroactive steroids: an update of their roles in central and peripheral nervous system

After five editions, the congress on "Steroids and Nervous System" held in Torino, Italy, represents an important international event for researchers involved in this field aimed to recapitulate mechanisms, physiological and pharmacological effects of neuroactive steroids. The present review introduces manuscripts collected in this supplement issue which are based on new interesting findings such as the influence of sex steroids on cannabinoid-regulated biology, the role of steroids in pain, the importance of co-regulators in steroidal mechanisms and the understanding of new non classical mechanism, the emerging role of vitamin D as a neuroactive steroid and the pathogenetic mechanisms mediated by glucocorticoid receptors. Finally, we have integrated these aspects with an update on some of the several and important observations recently published on this hot topic.